Compensating disk tension controller

ABSTRACT

An improved tension controller for a strand to achieve constant downstream tension regardless of tension variation in the upstream strand has a pair of tensioning plates ( 9, 10 ) between which the strand upstream ( 3 ), downstream ( 5 ) is compressed, generating frictional force for added tension. A selectable loading force is applied to the controller in the opposite direction to the movement of the strand. This loading force acts on a wedge between a movable tensioning plate and a fixed plate ( 9 ). The angle between the fixed plate ( 9 ) and the strand between the tensioning plates generates a compression force at a right angle toward the compressed strand for added tension. The incoming strand is deflected before it reaches its compressed stage between the tensioning plates. This strand deflection generates a force-component in the direction of the strand movement and reduces the loading force correspondingly. By proper selection of the wedge angle, the reduction of the loading force results in a reduction of the added tension by the same amount.

This is a national phase application of International ApplicationPCT/GB03/002577, filed Jun. 13, 2003, and claims priority to U.S. patentapplication Ser. No. 60/389,777, filed Jun. 19, 2002. This inventionrelates to an apparatus and method for controlling the tension in movingyarns. More specifically, it compensates for varying tension over thetime of a process and results in consistent strand tension, which isoften desirable for the next downstream process.

Numerous types of tension devices are known for the purpose ofincreasing the tension in a travelling strand. These include mostlydevices which add tension to the traveling yarn. Some of them applypressure to the traveling yarn, which in turn adds tension, based on theproduct of applied force times the friction coefficient. Others deflectthe traveling strand around one or several posts and through thesedeflections increase the tension depending on the bending angle and thefriction coefficient between the traveling strand and the bendingsurface.

More sophisticated strand tensioning systems use complex and expensiveelectronic means to measure the strand tension and electronically varythe applied tension with a close-loop feedback to achieve constantoutput tension. Their high cost prohibits their application for most,but extremely sensitive applications.

The invention disclosed in this application employs a tension deviceconsisting of two friction plates between which the strand travels. Itachieves constant output tension by reducing the applied tension betweenthese two friction plates by the same value as the amount of upstreamtension of the yarn. Since the total downstream tension is the sum ofthe tension upstream of the tension device and the tension added by thetension device, the downstream tension in the disclosed invention isconstant.

In accordance with a first aspect of the present invention there isprovided a strand tension apparatus, comprising:

(a) a strand delivery mechanism for delivering a moving strand (3)downstream from a strand supply (2);

(b) a strand take-up mechanism (7) positioned downstream from the stranddelivery mechanism for pulling the strand (5) from the strand supply;

(c) a tension controller (1) positioned between the strand deliverymechanism and the strand take-up mechanism for adding tension to themoving strand as it moves downstream to the strand take-up mechanism,the tension controller including a pair of tensioning plates consistingof a stationary tensioning plate (9) and a second, movable tensioningplate (10), between which plates the moving strand passes; and

(d) an adjustable loading force applied to the movable tensioning platein opposite direction to the movement of the strand generating throughgeometric restriction a force component perpendicular to the directionof the moving strand perpendicular to the direction of the moving strandin the region of the tensioning plates; and

(e) means to deflect the upstream strand entering the tensioncontroller, generating in the tension controller a deflection force ofwhich a force vector is directed in opposite direction of the adjustableloading force for a reduction of the added tension to the strand.

For further details of how we define the apparatus in terms ofprotective scope the reader is now referred to claims 2-11 hereafter.

In a preferred method of this invention, a wedge is pushed between afixed cam-surface and one of the two friction plates which in turnpinches the moving strand with the second, fixed friction plate. Themoving strand is deflected around the movable friction disk and itsupstream tension opposes the pushing force of the wedge, hence reducingthe compression force on the moving strand. A constant output tension isachieved by selecting the proper ramp angle for this wedge.

Preferably there is provided a strand tension controller for maintainingsubstantially uniform strand tension for delivery to a downstream strandprocessing station.

Preferably there is provided a strand tension controller which allows toset a desired tension level and tension uniformity downstream from thestrand tension controller.

Preferably there is provided a strand tension controller which includesmeans for uniformly and simultaneously setting the strand tension on aplurality of yarns being processed.

Preferably there is provided a multiple set of strand tensioncontrollers for which the desired tension level in all yarns can bechanged simultaneously to fit a specific need in a downstream strandprocessing station.

Preferably there is provided a multiple set of strand tensioncontrollers for which the desired tension level in all yarns can bechanged simultaneously. Preferably the arrangement is such that eachunit can be fine-adjusted individually to make it suited for specificneeds in a downstream strand processing station.

These and other features of the present invention can be achieved,wholly or in part, by providing a strand tension controller withprovision for reducing a compression force of the tension controller tothe strand to achieve a desired tension. If the incoming strand has notension, the full compression force is applied by the tension controllerto the yarn. If the incoming strand has tension, the compression forceis accordingly reduced.

The compression force may be provided to the tension device bymechanical means.

The compression force may be provided to the tension device by fluidicmeans.

The compression force may be provided to the tension device byelectrical means.

The compression force may be provided to the tension device by means ofpermanent magnets.

In the preferred embodiments disclosed below there is provided amechanical strand tension controller, comprising a strand guidingentrance which partially deflects the incoming strand around the movabletensioning plate and guides the strand between a stationary tensioningplate and a movable tensioning plate, a force applying spring, a wedgebetween the movable tensioning plate and a stationary cam surface and astrand exiting guide. The spring pushes the wedge between the fixed camsurface and the movable tensioning plate and exerts a compression forceon the traveling strand between the two tensioning plates. Thecompression force of the spring may be partially relieved through theresulting deflection force of the incoming strand to achieve asubstantially constant output tension in the downstream strand.

Preferably the invention uses common tension-disks, as used in mosttension devices.

The invention will now be further described, by way of example, in theaccompanying drawings, in which:

FIG. 1 is a perspective view of the tension controller according to oneembodiment of the invention;

FIG. 2 is an overall perspective view of the tension controller with aview of the path of the strand from the supply to the take-up accordingto an embodiment of the invention;

FIG. 3 is a side view of the tension controller with the strand exitingto the left;

FIG. 4 is a top view of the tension controller with the top part removedto show the inside of the tension controller;

FIG. 5 is an exploded view of the tension controller with all partsshown. Center lines connect the individual parts to facilitate theunderstanding of how the parts fit together;

FIG. 6 is a simplified cross-sectional view of the tension controllerwith the inserted strand and the adjustable loading force applied to awedge;

FIG. 7 is a force diagram with zero upstream tension and shows how theloading force is generating the compression acting on the tensioningplates;

FIG. 8 is a force diagram with nominal upstream tension and shows howthe loading force is reduced by the upstream tension;

FIG. 9 is a sectional front view of the tension controller with centralsetting of the loading force through an air tube;

FIG. 10 is a sectional front view of the tension controller with centralsetting of the loading force through electromagnetic force;

FIG. 11 is a sectional front view of the tension controller with thesetting of the loading force through a permanent magnet;

FIG. 12 is an alternate method with the wedge of FIG. 6 being replacedby linkages, achieving similar force characteristics;

FIG. 13 is a perspective view of the tension controller according to oneembodiment of the invention with a floating guide touching thetensioning plate;

FIG. 14 shows the forces and angles thereof reacting on the tensioncontroller;

FIG. 15 shows how the tension controllers can be centrally controlled bya common electrical supply.

Referring now specifically to the drawings, a tension controller 1 isbroadly illustrated in FIG. 1 as a part of a strand tension apparatus,including a strand supply and take-up mechanism. A supply package 2dispenses of the upstream strand 3 which enters into the tensioncontroller 1 through an entrance guide 4. The downstream strand 5 exitsthe tension controller 1 through the exit guide 6 to be wound up by thetake-up package 7.

Referring now to FIG. 2, a perspective view shows the tension controller1 having a bracket 8, shown transparent for clarity. A stationary disk 9is shown, located below a movable disk 10. A wedge plate 11 is locked inplace inside the movable disk 10. A setting spring 12 is held on oneside by a set-screw 13 which is inserted in a bore in the bracket 8. Theother side of the setting spring 12 pushes against the wedge plate 11.Two balls 14 are located between a wedge slot 15 in the wedge plate 11on one side and in a bracket slot 16 in the bracket 8 in order to reducethe friction between the fixed bracket 8 and the sliding wedge plate 11,which in turn is fastened to the movable disk 10.

In FIG. 3 the same parts are shown in front view. Especially noteworthyis the wedge angle 23, which plays an important role in the function ofthe tension controller.

Referring now to FIG. 4, a top-section of the tension controller 1 isshown with the top part of the bracket 8 removed.

FIG. 5 is an exploded view of the tension controller 1 with all partsshown. Center lines connect the individual parts to facilitate theunderstanding of how the parts fit together. It also shows theself-adjusting mounting of the stationary disk 9 which fits with itscenter hole 18 onto the bracket horn 17 of the bracket 8. This assuresan even contact between the two contact surfaces 19 of the stationarydisk 9 and the movable disk 10.

Referring to FIG. 6, a schematic drawing of the tension controller showsthe tension wedge 21 symbolizing the wedge plate 11 (not shown). Theshaded surfaces 22 are stationary surfaces. The adjustable loading force20 is acting on the tension wedge 21 which has a wedge angle 23. Theupstream strand 3 is bent around the movable disk 10 and is compressedbetween the movable disk 10 and the stationary disk 9 and the downstreamstrand 5 proceeds to the take-up package 7 (not shown).

The schematic drawing FIG. 7 of the tension controller 1 together with aforce diagram 29 demonstrates how the adjustable loading force 20 isacting on the tension wedge 21. The loading force 20 is broken down intothe two force components, a normal force 24 and a compression force 26.The normal force 24 is taken up by the stationary surface 22 and has noeffect on the strand 25. The compression force 26 acts on the strand 25by compressing it between the movable disk 10 and the stationary disk 9.It should be noted that the force angle 27 is equal to the differencebetween 90° and the wedge angle 23. The symbol 28 denotes a right angleof 90°. It is assumed in this drawing that the upstream strand 3 haszero tension.

Referring to FIG. 8A the same adjustable loading force 20 is acting onthe tension wedge 21. In addition it shows the up-stream tension 30 inthe upstream strand 3 with its resulting strand tension 31. It should berealized that the value of the strand tension 31 is larger than thevalue of the up-stream tension 30 due to the frictional forces addedduring the passing of the strand 5 around the movable disk 10.

FIG. 8B shows the force triangle of the adjustable loading force 20 withforce angle 27, resulting in a compensation force 25.

As shown in FIG. 8C, the force reduction 32 is accomplished by theadjustable loading force 20 which is reduced by the component of thestrand tension 31.

FIG. 8D demonstrates through the resultant force diagram 33 how thereduced loading force 34 results in a reduced normal force 35 with theconsequence of a reduced compression force 36.

Referring now to FIG. 9, the wedge plate 11 is loaded by an air pressuresystem. A U-channel 37 contains an elastic air tube 38. It pushes overthe pressure anvil 39 through a pressure stem 40 with a ball enlargement41 against a hole 45 in the wedge plate 11. The pressure anvil 39 isprovided with a tap 43 and the pressure stem 40 has a thread 42 which isthreaded into the tap 43. An adjustment wheel 44 on the pressure stem 40allows fine adjustment of the adjustable loading force 20 of eachindividual tension controller 1. By changing the air pressure in theelastic air tube 38 the adjustable loading force 20 (not shown) on anumber of individual tension controller 1, connected to the same airsystem can be varied simultaneously.

Referring now to FIG. 10, the wedge plate 11 is loaded byelectromagnetic force. An electromagnet spool 46 is mounted on thebracket 8. An anvil disk 47, with a disk tap 48, transmits the forcethrough the magnet stem 49, with a stem ball 50, against the hole 45 inthe wedge plate 11. Each tension controller 1 can be individuallyadjusted by turning the anvil disk 47 against the magnet stem 49.Changing the voltage of the electrical supply to the electromagnet spool46 a number of individual tension controller 1, connected to the sameelectrical system, can be varied simultaneously.

Referring now to FIG. 11, the wedge plate 11 is loaded by a permanentmagnet 51. The permanent magnet 51 is mounted on the bracket 8. An anvildisk 47, with a disk tap 48, transmits its force through the magnet stem49, with a stem ball 50, against the hole 45 in the wedge plate 11. Thetension controller 1 can be adjusted by turning the anvil disk 47against the magnet stem 49.

The tension controller 1 in FIG. 12A achieves the same forcecharacteristics as shown in FIGS. 6 to 8A-D with pivotal levers 52. Eachpivotal lever 52 is pivotally mounted on the stationary surface 22 onone side and on the movable disk 10 on the other side.

FIG. 12B demonstrates that the same force diagram 29 as in FIG. 8Bapplies also to this system.

Referring to FIG. 13, a floating guide 53 is pushing against the movabledisk 10 in order to treat the strand 3 more gently. The disk lever 54with the floating guide 53 is pivotally mounted on the bracket 8 by thepivot 55.

FIG. 14 shows the forces as they apply to the tension controller 1. Forthis tension analysis the tension controller 1 is shown with thefloating guide 53 as shown in FIG. 13. The upstream strand 3 is guidedaround the floating guide and the strand 26 is compressed between thestationary disk 9 and the movable disk 10. The adjustable loading force20 is applied to the tension wedge 21. By selecting the proper wedgeangle “α” for each input angle “β” the tension controller “1” becomesfully compensating for constant output tension 58. It is believed thatthe following formula is applicable:tan α=−μ+2μ(e ^(μβ)−cos β)/(e ^(μβ)−1)It is understood that “μ” is the friction coefficient between the strand26 and all surfaces it contacts. It is also understood that if “μ” isnot constant, the formula for “tan α” has to be modifiedcorrespondingly.

With respect to FIG. 15, several tension controllers 1 are shown wherethe electromagnetic spool 46 of each tension controller 1 is connectedto a central wiring 59 by means of the branch wiring 60. By changing thevoltage in the central wiring, all tension controllers 1 can be setsimultaneously.

1. A strand tension apparatus, comprising: (a) a strand deliverymechanism for delivering a moving strand downstream from a strandsupply; (b) a strand take-up mechanism positioned downstream from thestrand delivery mechanism for pulling the strand from the strand supply;(c) a tension controller positioned between the strand deliverymechanism and the strand take-up mechanism for adding tension to themoving strand as it moves downstream to the strand take-up mechanism,the tension controller including a stationary tensioning plate and amovable tensioning plate, between which plates the moving strand passes;(d) an adjustable loading force applicator for applying a loading forceto the movable tensioning plate in a opposite direction to the movementof the strand and thereby generating through geometric restriction aforce component perpendicular to the direction of the moving strandbetween the stationary tensioning plate and the movable tensioningplate; (e) an input strand deflector for deflecting the upstream strandentering the tension controller and generating a deflection force thatis a function of the tension of the strand as delivered from the stranddelivery mechanism; and (f) a tension adjuster positioned to be actedupon by the input strand deflector for generating in the tensioncontroller a deflection force directed in an opposite direction to theadjustable loading force for reducing the tension applied by the tensioncontroller.
 2. A strand tension apparatus according to claim 1, wherethe tension applied to the strand by the compression force between thetwo tensioning plates is reduced through the force vector of the tensionin the upstream strand sufficiently to result in a constant outputtension in the downstream strand.
 3. A strand tension apparatusaccording to claim 1 or 2, where the movable plate is restricted in itsmovement from the stationary plate by a major motion-component in thedirection of the down-stream movement of the strand.
 4. A strand tensionapparatus according to claim 1, wherein the tension adjuster comprises awedge between the movable tensioning plate and a fixed cam-surface.
 5. Astrand tension apparatus according to claim 4, wherein the wedge isfastened to the movable tensioning plate with the thinner portion of thewedge pointing in the opposite direction of the movement of the strand;and where the adjustable loading force pushes the wedge against thefixed cam-surface, forcing the movable tensioning plate against thefixed tensioning plate to apply the compression force to the movingstrand to increase the downstream tension.
 6. A strand tension apparatusaccording to claim 4, wherein at least one rolling member is positionedbetween the wedge and the fixed cam-surface to reduce the frictionbetween these two members.
 7. A strand tension apparatus according toclaim 1, where the upstream tension vector of the moving strand isdeflected before entering the space between the two tensioning plates togenerate a force opposing adjustable loading force to reduce the tensionon the movable strand.
 8. A strand tension apparatus according to claim1, wherein the movable plate is restricted in its movement to separatefrom the stationary plate by at least one pivoting link (52).
 9. Astrand tension apparatus according to claims 4 or 8, comprising at leastone pivoting link, fastened on one side to the movable tensioning plateand on the other side at a fixed point; wherein the adjustable loadingforce pushes the movable plate against the fixed cam-surface, forcingthe movable tensioning plate against the fixed tensioning plate to applythe compression force to the moving strand to increase the downstreamtension.
 10. A strand tension apparatus according to claim 1, whereinthe movable strand is guided around the movable plate through a floatingguide which is free to float in the general direction of the movingstrand between the tensioning plates.
 11. A strand tension apparatusaccording to claim 1, wherein the adjustable loading force is generatedby a spring.
 12. A method of controlling strand tension in a movingstrand, comprising the steps of: (a) feeding the strand downstreambetween a pair of tensioning plates of a tension controller to add dragto the strand; (b) apply a loading force to the tension controller in adirection opposite to the movement of the strand between the tensioningplates; (c) generating through geometric restriction of the loadingforce a compression force on the pair of tensioning plates to generateadditional drag on the strand; (d) deflecting the strand leading intothe tension controller to generate a force-vector of the upstreamtension in the strand in the same direction as the movement of thestrand between the tensioning plates, and subtracting the force vectorfrom the loading force to reduce in the added drag force, based on themagnitude of the upstream tension of the strand.